に当(あ)たる

As mentioned in our 当(あ)たり lesson, 当(あ)たる often has a meaning that is similar to に対(たい)して 'to be in regard to'. Due to this, when combined with the case marking particle に, に当(あ)たる will be translated as 'to correspond to', 'to amount to', 'to be appropriate for', or 'to be in regard to'. These may seem quite different, but we will examine the similarities shortly.
To use に当(あ)たる, attach it to the end of an (A) noun that you would like to mark as being the 'point of reference'. (B) may come directly after に当(あ)たる, or earlier in the sentence, so long as it is clearly separated from (A).

• 英語(えいご)の「what's up」は日本語(にほんご)の「元気(げんき)」に当(あ)たる表現(ひょうげん)だ。
  'What's up' in English corresponds to the expression 'genki' in Japanese.
• その人(ひと)は私(わたし)の親戚(しんせき)に当(あ)たる人(ひと)です。
  That person is my relative.
• 先生(せんせい)はタナカ君(くん)のいとこに当(あ)たる。
  The teacher is Tanaka-kun's cousin.
• 今年(ことし)は仕事(しごと)を始(はじ)めてから5年目(ねんめ)に当(あ)たる。
  This year amounts to the 5th year since I've started working. (It's been 5 years since I've started this job)

As for the link between に対(たい)して and に当(あ)たる, it is as follows. In に対(たい)して, (A) and (B) exist simultaneously, but (B) opposes something about (A). に当(あ)たる, (A) and (B) exist simultaneously, but (B) matches something about (A). Due to this, unless the speaker is specifically trying to highlight something that is 'opposing', or 'matching', the base meaning of '(A) and (B) existing simultaneously' may be the standard translation.

• ハクは納豆(なっとう)を食(た)べるのが好(す)きなのに対(たい)して、チヒロは納豆(なっとう)があまり好(す)きじゃない。
  As opposed to Haku who likes eating natto, Chihiro does not like eating it as much.
• 「Hello」は日本(にほん)で「こんにちは」に当(あ)たる言葉(ことば)です。
  'Hello' corresponds to the Japanese word 'konnichiwa'.